微波真空干燥技术在食品中的应用

<正> 微波是一种波长为1mm～1m,频率在300～300,000MHz之间的电磁波,近年来被广泛应用于食品加工中,成为生产干燥食品的一项高效技术。 加热原理 微波的加热方式与普通的热传递大不相同。微波能够穿透到物质的深层,使物质的内外同时加热升温。对于这种加热机理,目前较合理的解释是,因为高频电场在空间不断地变换方向,使被加热物中的极性分子以每秒上亿次的速度振动,这些分子间的     

微波处理技术在食品干燥领域中的应用

文章主要分析了微波处理技术的机理和特点,与传统干燥方式相比,微波处理作用下,物料微观结构出现较多的孔隙和较少的坍塌,有利于水分的脱除,增加了对流传质速率,降低了干燥能耗,提高了营养成分的保存率。同时也比较了微波干燥处理、微波在联合干燥和辅助干燥过程中的应用,对比分析了其干燥能耗、干燥时间和物料品质,并展望了微波处理技术在食品干燥领域良好的发展前景。     

微波干燥食品技术

微波干燥具有突出的优点和特点,新的应用也层出不穷。本文阐述了微波干燥、微波／热风干燥、微波／真空干燥、微波／冷冻干燥及在食品工业中的一些应用。     

微波干燥技术在食品工业中的应用

本文介绍了微波干燥技术的原理，微波干燥的特点以及目前微波干燥技术在食品工业中的应用现状，并提出微波能发展的意见     

食品微波真空干燥技术研究进展

微波真空干燥是用微波辐射作为加热源在真空条件下进行加热而使物料脱水的过程,具有快速、高效、低温等优点。本文阐述了微波真空干燥的作用机理,介绍了微波真空干燥的特性及研究现状,旨在为微波真空干燥技术在食品加工中的研究和应用提供参考。     

热泵微波联合干燥及其在农副产品干燥中的应用

本文对热泵微波干燥的实用性及其性能进行了模拟分析和试验研究。试验及计算结果吻合较好。分析了空气旁通率、压缩机转速及空气质量流量等主要设计及运行参数对干燥性能的影响。与蒸汽加热干燥比较的结果表明：通过精心设计，可使热泵微波干燥系统的能耗与蒸汽加热干燥。     

微波干燥技术在筒子纱线中的应用

自行研制微波于燥设备并用其干燥筒子纱卷,研究微波干燥设备的干燥效率及干燥效果,探讨其在纺织染整行业应用的可行性,为微波干燥在纺织染整行业的应用提供研究基础.经实验发现,微波干燥筒子纱的效率高于1.1 kg(水)/(kW·h)(微波).微波干燥后,纱卷含水均匀,纱线的强力和手感得到改善,微波干燥节能效果显著,比射频节能2...     

热泵微波联合干燥及其在农副产品干燥中的应用

本文对热泵微波干燥的实用性及其性能进行了模拟分析和试验研究，试验及计算结果吻合较好。分析了空气旁通率、压缩机转速及空气质量流量等主要设计及运行参数对干燥性能的影响，与蒸汽加热干燥比较的结果表明：通过精心设计，可使热泵微波干燥系统的能耗与蒸汽加热干燥相当。     

微波干燥技术在金银花烘干中的应用研究

介绍了应用微波技术干燥金银花的工作原理、实验装置,重点对金银花的干燥方式、方法、效果以及干燥功率、效率等进行了探索性研究,在金银花得到干燥的同时,保持色、香、形基本不变,提高了金银花的规格等级和加工效率。     

The variable nature of Biot numbers in food drying

Biot numbers (Bi) relate internal and external resistances to mass or heat fluxes and are useful to identify controlling mechanisms. Their variation during drying received little attention despite its importance in model selection. Therefore, variable Bi were analysed in drying of wheat, a low-moisture product, and in the formation of a low-calorie, dehydrated apple-leather (LCAL), a high moisture product. Wheat drying was predicted with a numerical solution from a m.c. of 0.35 kg water/kg dry matter, to find a variable mass transfer Bi that shifted the controlling mechanism from internal-external to internal. From a lower m.c. of 0.205 kg water/kg dry matter, the entire process was internally controlled. Drying of shrinking LCAL was solved with the energy balance. The mass transfer Bi varied from 0.5 to 1600, while the heat transfer Bi, only from 0.25 to 0.5, and a modified version, from 0.25 to 0.     

热泵式流化床干燥装置及其应用优势

热泵式流化床干燥装置干燥食品的突出优点是节能和食品干燥质量好。本文对热泵式流化床干燥食品的特点进行了简要介绍，对热泵式流化床的结构性能进行了较深入的分析。对这种新型装备的推广与普及所需解决的问题及其技术思路进行了探讨，并对热泵式流化床食品干燥成套装备的市场应用前景进行了预测。     

Effect of food ingredient on microwave freeze drying of instant vegetable soup

The objective of this work was to study the effect of three different food ingredients viz. NaCl content (1-15 g/100 g water), sucrose content (5-25 g/100 g water) and sodium glutamate content (0.5-10 g/100 g water) on microwave freeze drying (MFD) of instant vegetable soup. Response surface methodology (RSM) was employed to optimize their addition levels in instant vegetable soup for MFD. Finally, a comparison of MFD for instant vegetable soup with and without added ingredients was carried out. The results showed that NaCl content and sucrose content had significant influence on drying time and sensory quality, while sodium glutamate content had insignificant effect. The optimum ingredients of the instant vegetable soup for MFD were: NaCl content of 3.2-5.3 g/100 g water, sucrose content of 2-6.8 g/100 g water and sodium glutamate content of below 4.5 g/100 g water. Comparing with MFD vegetable soup without ingredients, condiments addition could increase drying rate and shorten drying time.     

Microwave freeze drying of sea cucumber (Stichopus japonicus)

Freeze drying (FD) yields the best quality of dried sea cucumber but at the cost of long drying time and also the overall cost. Air drying (AD) gives an unacceptably poor quality product. To achieve faster drying along with a high quality product a microwave freeze drying (MFD) technique was developed to dry sea cucumbers. The relationship between corona discharge and microwave power at various pressures and initial moisture content conditions was studied to avoid the possibility of corona discharge during MFD. According to the drying characteristics of MFD, a control strategy for the MFD process was also developed. MFD reduced the drying time by about half of conventional FD process and provided a similar good product quality.     

Power density control in microwave assisted air drying to improve quality of food

Currently, the new trend is the development of microwave hot air drying control in order to solve the problem of hot spots on the product. So in this study, a microwave/hot air drying system with the ability of automatic power density control was developed for tomato drying. Three power densities (3, 5 and 7 W/g) at 40 °C air temperature were applied and the output, reflected microwave power and the mass of the sample were registered online. Two different drying strategies were implemented. The first consisted of a microwave drying without specific power control. The second one introduced power control. A feedback control based on specific power related to the actual sample mass resulted in the best power control and the improvement of product quality compared to the dry sample without power control.     

微波技术在烟草工业中的应用研究进展

详细介绍了微波技术在烟草化学、烟草工艺以及烟草检测等方面的应用研究进展 ,展望了微波技术在烟草工业中的应用前景 ,并提出了微波技术应用于烟草工业中急需解决的几个技术问题。     

Optimal power control strategies in microwave drying

A microwave drying system, which can automatically and continuously adjust microwave power, control sample temperature and measure sample mass, was developed and used in apple drying. At three drying temperatures, i.e., 75, 65, 55 °C, applied microwave power was recorded and analyzed, and a relationship of the power with respect to drying rates was built. With this relationship, apples were further dried at the same three temperatures but using variable power during drying process based on the online obtained drying rates. A better temperature control was achieved and less energy was consumed with this method. Depending on the resulted power profiles, a linear and a three-step power control methods were further developed to simplify the control system. With the developed methods, mass measurements were no longer required and power control could be easily implemented, while temperature control and energy consumption were still acceptable.     

Microwave drying characteristics of potato and the effect of different microwave powers on the dried quality of potato

Little detailed information is available on the microwave drying characteristics of potato and the use of different microwave powers to dry food products. Experiments were conducted to study the microwave drying characteristics and the dried quality of potato. The study focuses on describing the microwave drying characteristics of potato and discussing the effect of sample thickness, drying power and mass. The results show that if the power level increases, the mass load decreases and the thickness of the sample decreases, the dehydration rate increases and the drying energy consumption decreases. There are two falling rate periods during microwave drying of potato: the first falling rate period is for a moisture content of more then 1.1 (dry basis, DB); the second falling rate period is for a moisture content of less than 1.1 (DB). The same water loss will consume more energy when the moisture content is less than 1.1 (DB). A two-stage drying process was employed during microwave drying of potato. The microwave power of the first drying stage differed form that of the second drying stage. The moisture content of the breakpoint for the conversion of the first drying stage into the second drying stage is a moisture content of 1.1 (DB). A quadratic orthogonal regression experiment was conducted, and the effects of slice thickness, the first drying load power and the second drying load power on sensory quality, the rehydration ratio and the energy consumption rate were established. The slice thickness, the first drying load power and the second drying load power linearly affected the three indices. The effect of the product of the second drying load power and the potato slice thickness on the rehydration ratio and the energy consumption rate is significant. The optimum drying parameter combination for the three indices was obtained. The rehydration ratio of the dried products decreased with an increase of the second drying load power and the slice thickness. The concave curves of the sensory quality versus the three factors were shown.     

Drying rate control in the middle stage of microwave drying

Microwave drying of apples at constant temperatures follows typical drying curves. The middle stage of the drying process shows a faster drying rate and accelerated moisture evaporation. Meanwhile, more flavors are lost, surface color is degraded, and charring often occurs in this stage. To improve the drying effects, drying curves were controlled and changed in this study. The drying curve was linearized by automatically varying drying temperatures in the middle stages. The controlled drying process therefore led to an optimized temperature profile. To simplify the drying methods, apples were further dried with the obtained temperature profile, while drying curves were online monitored but not controlled. It was proved that slowing down the drying rate in the middle stage could improve the product quality in terms of color, flavor, and overall appearance, while the drying time and energy consumption were still acceptable (within 200 min and 22 kJ/g, respectively).     

均匀平铺载荷下微波干燥室内的能量分布

对均匀平铺的典型载荷条件下微波干燥室的能量分布特性进行了研究。根据实验数据分析可知当具有较大的介电常数的物料均匀平铺在干燥床上时 ,微波干燥室内的能量分布可根据天线的辐射能分布瓣型来确定。理论上 ,在微波干燥床上的XZ面内的θ=± 2 4°50′50″范围内及YZ面内的θ =± 36°2′40″范围内的微波功率密度大于该面内最大微波功率密度的二分之一